MAX4358ECE MAXIM [Maxim Integrated Products], MAX4358ECE Datasheet - Page 38

• Manufacturer Part Number: MAX4358ECE
• Description: 32 x 16 Nonblocking Video Crosspoint Switch with On-Screen Display Insertion and I/O Buffers
• Manufacturer: MAXIM [Maxim Integrated Products]

32 x 16 Nonblocking Video Crosspoint Switch
with On-Screen Display Insertion and I/O Buffers
Resistor vs. Capacitive Load. A lowpass filter is created
from the series resistor and parasitic capacitance to
ground. A single R-C do not affect the performance at
video frequencies, but in a very large system there may
be many R-Cs cascaded in series. The cumulative
effect is a slight rolling off of the high frequencies caus-
ing a "softening" of the picture. There are two solutions
to achieve higher performance. One way is to design
the PC board traces associated with the outputs such
that they exhibit some inductance. By routing the traces
in a repeating "S" configuration, the traces that are
nearest each other will exhibit a mutual inductance
increasing the total inductance. This series inductance
causes the amplitude response to increase or peak at
38
Table 7. 7-Bit Serial Control Word Bit Assignments (Mode 1: Complete Matrix Mode
Programming)
Figure 9. Improved Implementation of On-Screen Display
SYNC15
SYNC0
SYNC1
CAMERAS
6 (MSB)
0 (LSB)
______________________________________________________________________________________
MEMORY
BIT
5
4
3
2
1
OSD
OSD
OSD
COMPUTER CONTROL
OSDFILL15
OSDKEY15
OSDFILL0
OSDFILL1
OSDKEY0
OSDKEY1
IN31
Input Address 4
Input Address 3
Input Address 2
Input Address 1
Input Address 0
IN0
IN1
Output Enable
Gain Set
NAME
MAX4358
OUT0
OUT1
OUT15
SYNC0
SYNC15
SYNC1
Enable bit for output, 0 = disable, 1 = enable.
Gain Select for output buffer, 0 = gain of +1V/V, 1 = gain of +2V/V.
MSB of input channel select address.
LSB of input channel select address
MONITOR
MONITOR
MONITOR
higher frequencies, offsetting the rolloff from the para-
sitic capacitance. Another solution is to add a small-
value inductor to the output.
The MAX4358 facilitates the insertion of on-screen
graphics and characters by using the built-in fast 2:1
multiplexer associated with each of the 16 outputs
(Functional Diagram). This mux switches in 40ns, much
less than the width of a single pixel. Access to this fast
mux is through 16 dedicated OSDFILL analog inputs
and 16 dedicated OSDKEY input controls. OSD timing
is externally controlled and applied to the OSDKEY
inputs (Figure 1). Pulling OSDKEY i low switches the
signal on the OSDFILL
the OSDKEY signal is logic high, the signal at IN_ is
switched to the output. This switching action is repeat-
ed on a pixel-by-pixel basis for each scan line. In this
way any synchronized video signal, including arbitrary
graphics, can be inserted on the screen (Figure 9).
This technique for inserting OSD display information is
an improvement over the way it has traditionally been
done. Other OSD techniques require an external fast
mux and a buffer for each output.
Improper signal routing causes performance problems.
The MAX4358 has a typical crosstalk rejection of
-62dB at 6MHz. A bad PC board layout degrades the
crosstalk rejection by 20dB or more. To achieve the
best crosstalk performance:
1. Place ground isolation between long critical signal
PC board trace runs. These traces act as a shield to
potential interfering signals. Crosstalk can be
degraded from parallel traces as well as directly
above and below on adjoining PC board layers.
Crosstalk and Board Routing Issues
FUNCTION
On-Screen Display Insertion
i
input to the OUT
i
output. When